A 5.8 GHz 1.77mW AFSK-OFDM CMOS Backscatter Transmitter for Low Power Internet of Things Applications

This paper presents an AFSK-OFDM (amplitude frequency shift keying-orthogonal frequency division multiplexing) based backscatter transmitter for Internet-of-Things (IoT) applications. The transmitter uses an array of 4 low-power direct digital frequency synthesizers (DDFSs) and DACs to transmit data using both frequency and amplitude symbols on 4 different OFDM subcarriers. The backscatter modulator is demonstrated within a 5.8 GHz wireless link using an 8-symbol OFDM library at a range of 2.7m and shown to consume 1.77 mW when operated at a symbol rate of 4MS/s (corresponds to 12 Mb/s). The modulator chip occupies 0.45mm² of silicon area.